 Good morning, dear student. I am Dr. Satchinar Gangze, Professor and Head, Department of Electronics Engineering in Vulture Institute of Technology, Sholab. Welcome to a class where today we are going to discuss about different database types. The learning outcome of this session at the end of this video lecture, student will be able to explain different type of databases. What is a data? We already know that the modern organizations, they create and stock vast amount of data through different storage methods. Data can be numerical, alpha numerical, alphabets, images, audios, videos. What is a data? We already defined data as an elementary description of things, events, activities, and transactions. And all this data is collected, recorded, classified, and stored, but not necessarily in an organized manner. So, a description of the thing, event or activities or transaction, we are calling it as a data. If we look at the difference between the data and the database, data is just an elementary description of thing, event, activities, or transaction, but not necessarily stored in an organized way. When we talk about the database, we say that the data items are stored in an organized or systematic way so that it will be easy for the retrieval of the data or some information can be generated out of these data items. If you look, for example, a data corresponding to a class where I have stored the role number of a student, then his name, then his address, and the gender of the student. So, if I store this data in a systematic way consisting of rows and columns, where rows corresponds to a record of a particular student, and column corresponds to the various attributes of that particular student, then this is a systematic way, a tabular way of storing the data. Storing the data in this manner can help me. For example, I want to know what is an address of the student whose role number is five. So, I can just go to over here, then I can see that the role number is five, then I can find out the address. Similarly, suppose I want to have an query where I need an information, how many boys and how many girls are there in the class, then I need to filter out the column of male and female and then through this database management system, I can find out how many boys and how many girls are there. So, storing the data in a systematic or organized way with that, it is easy for data for retrieval as well as it is if I require certain information that can be retrieved out of the database. Now, when we talk about the database, so once we understand the difference between data and a database, data is simply the description of the atom or the things or the event or the activities where database is nothing but storing all that data in a systematic way. Now, once we understand the difference between the data and database, we can say that there are different type of the databases, there are different rather ways to categorize the databases. The first way of categorizing or classifying the database is depend upon how the database is being designed and there are four popular types of the database. The first one is called the relational database in which it is an efficient at relating data or connecting data in different table and joining information from these different tables or different data atoms different located in different file. So, that kind of database is called as the relational database. The second type of the database is hierarchical database or the network database where there is a relationship between the parent and child relationship between different records and that kind of database is there are two types rather one is hierarchical database and the other one is a network database. There is another class of the database or type of the database called as an object oriented database and which uses object to represent the models of the database. So, in short, we can say that there are four type of the databases relational database, hierarchical database and network database and object oriented database. So, here please pause the video and answer the question what are the different type of the databases. Thank you and I think now you have already have already have answered with you that there are four type of the databases right. Now, let us go ahead and understand something more about these databases. Another way to classify the database is depending upon where the database is located and then there are two types of the database. The first one is called as the centralized database and the other one is called as the distributed database. Now, let us understand what is the difference between the centralized database and the distributed database. Look at over here. This is a centralized database. In case of centralized database, all related file are stored in one physical location, right. For example, at over here, you can see that there is a centralized large mainframe computer where all these data files is being stored. Now, this kind of arrangement where all the database or all database file are being stored at one single physical location centralized location, then it is called as the centralized database. The advantage of this centralized database is that the files are made more consistent, the database is more consistent as it is being located in a single location. And secondly, it can provide a security as we know that the data need to be protected and then we require certain security aspect like maybe it's it consists of a firewall. Now this security can be applied at a one single point please understand applying or providing the security is a costly affair. And if the entire database is located at a single point at a single location, then providing the security is security can be easy one. However, the there are as we see these are the two advantages of the centralized database that the files are consistent and the security can be provided at one single point. There are certain disadvantages of centralized database also the first disadvantage of centralized database is that it is if as everything is put in a single point and then that then if there is a failure of the single point database, then it can cause it can cause to catastrophic effect. Right as as there is a prover that don't put all your x into a single basket. So here we are putting the data in a single server or single location. And then there can be if that there is a failure of this, then it can have a very, very catastrophic effect on the organization database, right? The second problem with a centralized database is that the user which are located far away from the centralized database, whenever they want to access the database, it may be either an action query or a select query, whenever the user want to access the database, if the user accessing the database is located there. So we are talking about the physical or the geographical distance, right? So if they are located near to the database, then no problem there can be transaction, but the transaction they don't need to travel over a long distance. But especially we are if we are talking about the users which are which are physically or geographically located away from the database centralized database, then every transaction they initiate has to go to the centralized database. And in that case, there are a lot many transactions involved. And each of this transaction has to go to a centralized database. And then it can cause the delays. So the two problems that we can see or which are very evident from the centralized database is first as all the data is at a single point. And if that data fails, then it can have a it can have a catastrophic effect on the organization. Secondly, as we go away from the centralized database, the delay required for the transaction increases. Now in order to overcome the problems of the centralized database, we have another type of the database, which is called as the distributed database. Now here instead of putting the entire database into a single point, the database is divided and it is stored at a multiple location. So it may be stored in multiple computer located in the same physical location, or usually it may be stored at the different locations physical or geographical location. And then all these databases are connected through the network of the computer. When we talk about the distributed databases, there are two types of the database. The first is called as the replicated database and the second one is called as the partition database. Please understand both these replicated and partition database, they represent rather the same concept of distributed database. So these two replicated and partition database are the types of the distributed database. In case of the replicated database, the same data is made available or the replica of the same data is made available at the multiple locations or the computer. So there can be more data there can be more than one database, however, each of the database represent the same copy or rather represent a copy of the same database. Now this is the advantage of this kind of system is that yes, if one of the one of the database fails, then there is already copy available of the same database at a multiple location. And now as we have multiple databases, which can be one of this database can be located near to the user, then it improves the response time because we have seen that in case of centralized database, every query need to go to a centralized location. And if that location is away from the user, then it may require time. But now as we have a multiple databases, user can locate a nearby database and then the response time can be less. Now problems again, there are problems with the replicated database. There are two three problems. The first is that whenever there is a any transaction and one of the database is getting updated, all the copies located at the different location also need to be updated. And there is a lot of transaction happening over a data like the data can be added, deleted or modified updated. And in case of every transaction, all the copies of the data must be updated. Secondly, it is an expensive because as there are multiple location or multiple databases, maintaining them is also an expensive offer affair. You must have a physical infrastructure for that. At the same time, the security also be provided at the different location. Then there is another problem of the scheduling. Whenever there are multiple databases or copies of the same database at a multiple location, scheduling is required when which database should be updated depending upon the other databases. And that problem is called the scheduling problem. So we have seen that the second type is replicated, it do have certain advantages, but also certain disadvantages. The last type of the database is called as the partition database where the database is divided and a part of the database is located at one of the one of the database location. And the which database is how to divide the database into multiple parts and where to look at each part depending upon the local need. Now here we can combine the advantages of the centralized database and replicated database, because it will give a fast response time, and the file can be a file can be entered more quickly and keep more accurate without much updating or scheduling is required. And then the, of course, the security problem can be there because there it has a multiple location. So that is about the partition database. So with that, we come to the end of this session. And the references we have used for this, there are two books which I'm using. One is information technology for management by Turban Volvino. And the second one is information system by Rand Stier and John Stier-Laut. Thank you very much for listening. Have a good day.